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.IX Title "Imager::Expr::Assem 3pm"
.TH Imager::Expr::Assem 3pm 2024-04-13 "perl v5.38.2" "User Contributed Perl Documentation"
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.\" way too many mistakes in technical documents.
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.nh
.SH NAME
.Vb 2
\&  Imager::Expr::Assem \- an assembler for producing code for the Imager
\&  register machine
.Ve
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 2
\&  use Imager::Expr::Assem;
\&  my $expr = Imager::Expr\->new(assem=>\*(Aq...\*(Aq, ...)
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
This module is a simple Imager::Expr compiler that compiles a
low-level language that has a nearly 1\-to\-1 relationship to the
internal representation used for compiled register machine code.
.SS Syntax
.IX Subsection "Syntax"
Each line can contain multiple statements separated by semi-colons.
.PP
Anything after '#' in a line is ignored.
.PP
Types of statements:
.IP "variable definition" 4
.IX Item "variable definition"
.RS 4
.RS 4
\&\f(CW\*(C`var\*(C'\fR \fIname\fR:\fItype\fR
.RE
.RE
.RS 4
.Sp
defines variable \fIname\fR to have \fItype\fR, which can be any of \f(CW\*(C`n\*(C'\fR or
\&\f(CW\*(C`num\*(C'\fR for a numeric type or \f(CW\*(C`pixel\*(C'\fR, \f(CW\*(C`p\*(C'\fR or \f(CW\*(C`c\*(C'\fR for a pixel or
color type.
.Sp
Variable names cannot include white-space.
.RE
.IP operators 4
.IX Item "operators"
Operators can be split into 3 basic types, those that have a result
value, those that don't and the null operator, eg. jump has no value.
.Sp
The format for operators that return a value is typically:
.RS 4
.Sp
.RS 4
\&\fIresult\fR = \fIoperator\fR \fIoperand\fR ...
.RE
.RE
.RS 4
.Sp
and for those that don't return a value:
.Sp
.RS 4
\&\fIoperator\fR \fIoperand\fR
.RE
.RE
.RS 4
.Sp
where operator is any valid register machine operator, result is any
variable defined with \f(CW\*(C`var\*(C'\fR, and operands are variables, constants or
literals, or for jump operators, labels.
.Sp
The set operator can be simplified to:
.Sp
.RS 4
\&\fIresult\fR = \fIoperator\fR
.RE
.RE
.RS 4
.Sp
All operators maybe preceded by a label, which is any non-white-space
text immediately followed by a colon (':').
.RE
.SH BUGS
.IX Header "BUGS"
Note that the current optimizer may produce incorrect optimization for
your code, fortunately the optimizer will disable itself if you
include any jump operator in your code.  A single jump to anywhere
after your final \f(CW\*(C`ret\*(C'\fR operator can be used to disable the optimizer
without slowing down your code.
.PP
There's currently no high-level code generation that can generate code
with loops or real conditions.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBImager\fR\|(3), \fItransform.perl\fR, \fIregmach.c\fR
.SH AUTHOR
.IX Header "AUTHOR"
Tony Cook <tony@develop\-help.com>